Genetic control of cell behavior is a critical issue in the field of stem biology, where determining a cell fate or reprogramming adult somatic cells into pluripotent cells has become a common experimental practice. Despite scientific advances in the field, in order for these cells to have therapeutic clinical potential techniques for controlling gene expression need to be developed that minimize or eliminate the risk of oncogenesis and mutagenesis. Possible routes for achieving this outcome could come in the form of a transient non-viral gene delivery system or through the addition of small chemical molecules.
The efficient delivery of DNA using non-viral plasmid vectors has been a major challenge in the fields of gene therapy, stem cell research, cellular therapeutics and RNAi/oncology (Bleiziffer et al., 2007; Clements et al., 2007; Dalby et al., 2004; Goessler et al., 2006; {hacek over (S)}arić and Hescheler, 2008). Over the past decade, novel engineered materials have been developed along with quantitative physical characterization assays in an attempt to meet the highly efficient transduction capacity of viral vectors, such as retroviral and lentiviral systems, while maintaining a high level of safety, minimal toxicity, robustness for scale-up and the ability to carry large cargo (Clements et al., 2007; Douglas et al., 2006; Douglas, 2008; Douglas et al., 2008; Tsai et al., 2002). Recently, a transient gene delivery system was developed to deliver two fluorescent liver-specific reporter plasmids into differentiating, semi-mature murine embryonic stem (ES) cells for enriching a sub-population of hepatocyte-like cells (Wallenstein et al., 2008). The benefit of the transient expression of the plasmids fulfilled the system's needs, as the activation of the fluorescent reporters was only necessary prior to the completion of the cell sort. Despite the proof-of-concept of this concept, it was still limited by inherent low transfection efficiency (maximum≈56%) of plasmid expression. Improving the transfection efficiency to this population could dramatically improve the targeting of smaller subpopulations of cells to attain better sensitivity of expression values and to improve the recovery fraction. Recently, many groups have targeted adult somatic cells to generate induced pluripotent stem (iPS) cells by using retroviral vectors to express genes associated with pluripotency (Hanna et al., 2007; Meissner et al., 2007; Stadtfeld et al., 2008). Despite the success of these techniques, in order to realize the therapeutic potential of these cells in the future, the authors point out the need to develop alternate delivery methods that would minimize the risk of oncogenesis due to the random insertion of genes (Liu, 2008; Pera and Hasegawa, 2008). Such an approach may take the form of a transient gene delivery system or the use of small chemical molecules.